Integrally-formed reducer pipe and preparation process thereof

Abstract

The invention discloses an integrally-formed reducer pipe and a preparation process thereof, and relates to the technical field of pipe fitting machining. The specific preparation process comprises the following steps: casting a round billet by using an alloy, boring and carrying out hot extrusion to obtain a pipe, cutting into sections, carrying out extrusion forming to obtain a reducing blank pipe, and finally carrying out passivation and roller coating of an anticorrosive coating to obtain the reducing pipe. Wherein the alloy is obtained by smelting a copper-nickel alloy, a mixed nickel-calcium intermediate alloy, an aluminum-lanthanum intermediate alloy and iron sulfide; the alloy comprises the following chemical components in percentage by mass: 10.2 to 10.6 percent of Ni, 1.6 to 1.8 percent of Fe, 0.5 to 0.8 percent of Mn, 0.2 to 0.5 percent of Al, 0.01 to 0.05 percent of La, less than 0.0005 percent of C, less than 0.005 percent of Pb, less than 0.002 percent of S, less than 0.003 percent of P and the balance of Cu and inevitable impurities.

Description

Technical Field

[0001] The present invention relates to the technical field of pipe fitting processing, and specifically to an integrally formed reducing pipe and its preparation process. Background Art

[0002] Reducing pipes are widely used in fields such as marine, oil, petrochemical, and shipbuilding. As common fittings in ship pipeline systems, they are used to connect pipes with different diameters to achieve smooth fluid transmission. Since ships are often in a seawater environment, the material selection of reducing pipes is crucial. Reducing pipes are usually made of corrosion-resistant materials such as stainless steel, carbon steel, or alloy steel to ensure their long-term stability and reliability in the marine environment.

[0003] B10 copper-nickel alloy is widely used in seawater ship pipeline systems. Due to its excellent corrosion resistance and mechanical properties, it is suitable for ship components that are long-term exposed to seawater environment, and can effectively resist the erosion of corrosive media such as chloride ions and salt spray in seawater, thereby extending the service life of equipment and reducing maintenance costs. At the same time, it has high tensile strength, yield strength, and elongation, as well as good toughness, and can remain stable under dynamic loads and is not prone to fracture or deformation. Therefore, most reducing pipes on the market are made of B10 copper-nickel alloy material. However, in actual applications, when the ship is in operation, the salt, microorganisms, and dirt in seawater will adhere to the inside of the pipe, resulting in changes in fluid flow rate. And the reducing pipe adjusts the fluid flow rate and pressure by changing the pipe cross-sectional area, which will further exacerbate the impact of erosion. In order to improve the service life and reduce costs, the present invention proposes an integrally formed reducing pipe and its preparation process to address the above problems. Summary of the Invention

[0004] The purpose of the present invention is to provide an integrally formed reducing pipe and its preparation process to solve the problems raised in the prior art.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] A preparation process for an integrally formed reducing pipe, and the specific preparation process is as follows:

[0007] Step 1: Place a copper-nickel alloy ingot in a vacuum melting furnace, add nickel-calcium master alloy, aluminum-lanthanum master alloy, and iron sulfide for smelting, cast a round billet using a semi-continuous casting process, perform homogenization treatment after boring, and then obtain a pipe through hot extrusion. After cold rolling the pipe, it is fully annealed and straightened to obtain an alloy pipe blank.

[0008] Step 2: Cut the alloy pipe blank prepared in Step 1 into pipe sections, load them into a forming die, use a push rod to push the blank into the forming channel, and gradually extrude until the push rod disengages from the forming channel to obtain a reducing blank pipe.

[0009] Step 3: After annealing the reduced-diameter blank tube prepared in Step 2, perform polishing and cleaning, then immerse it in passivation solution a for 30 min, take it out, clean and dry it, then immerse it in passivation solution b for 30 min, take it out, clean and dry it, then immerse it in passivation solution b for 1 - 2 h, clean and dry it, and then roll coat an anti-corrosion coating on the inner and outer surfaces of the tube, and cure to obtain the reduced-diameter tube.

[0010] Among them, the chemical composition of the alloy tube blank prepared in Step 1 is calculated by mass percentage as follows: Ni 10.2 - 10.6%, Fe 1.6 - 1.8%, Mn 0.5 - 0.8%, Al 0.2 - 0.5%, La 0.01 - 0.05%, C < 0.0005%, Pb < 0.005%, S < 0.002%, P < 0.003%, and the balance is Cu and unavoidable impurities.

[0011] In Step 1, the homogenization treatment temperature is 800 - 950 °C, and the holding time is 2 - 3 h; the full annealing temperature is 700 - 750 °C, and the holding time is 1 - 2 h;

[0012] In Step 3, the annealing treatment temperature is 400 - 650 °C, the holding time is 1 - 2 h, and it is air-cooled to room temperature.

[0013] The preparation steps of passivation solution a in Step 3 are as follows: Mix and stir an aqueous solution of zinc nitrate hexahydrate and an aqueous solution of 2-methylimidazole for 30 min to obtain passivation solution a; the mass concentration ratio of zinc nitrate hexahydrate to 2-methylimidazole in passivation solution a is 1:(2 - 3).

[0014] The preparation steps of passivation solution b in Step 3 are as follows: Dissolve 2-methylimidazole and 2-aminobenzimidazole in deionized water, add an aqueous solution of zinc nitrate hexahydrate, and mix and stir for 30 min to obtain passivation solution b; the mass concentration ratio of zinc nitrate hexahydrate, 2-methylimidazole, and 2-aminobenzimidazole in passivation solution b is 1:(1.5 - 2):(0.1 - 0.3).

[0015] The preparation steps of the anti-corrosion coating are as follows:

[0016] Step s1: Take graphene oxide, ultrasonically stir it in deionized water for 1 h, then add hydrazine hydrate and mix, dropwise add ammonia water to adjust the pH to 10, heat it to 95 °C and stir for 5 h, filter by suction and then freeze-dry to obtain reduced graphene oxide, transfer it into urushiol, ultrasonically stir for 1 h, then add paraformaldehyde and rosin amine and mix, heat to 90 - 95 °C, keep warm and stir for 1 h to obtain modified graphene;

[0017] Step s2: Take the modified graphene prepared in Step 1, add polyether polyol and silane coupling agent, mix and stir for 30 min, then add isophorone diisocyanate, heat to 70 - 80 °C and preheat for 30 min, then add dibutyltin dilaurate and continue to react for 2 - 3 h, and cool to room temperature to obtain the anti-corrosion coating.

[0018] In step s1, the dosage ratio of paraformaldehyde, rosin amine and urushiol is (3 - 5) g : (15 - 18) g : 15 mL, and the addition amount of reduced graphene oxide is 2 - 5 wt% of urushiol; in step s2, the volume ratio of polyether polyol and isophorone diisocyanate is 1 : (1 - 2); the addition amount of modified graphene is 6 - 15 wt% of the anticorrosive coating.

[0019] The process parameters for curing the anticorrosive coating are curing at 60 °C for 12 h; when roller-coating the anticorrosive coating, the film thickness is controlled to be 100 - 200 μm.

[0020] An integrally formed stepped tube is processed by the above preparation process.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] 1. The tube blank prepared by the present invention is cast from a nickel-copper alloy, and nickel-calcium master alloy, aluminum-lanthanum master alloy and iron sulfide are added to further improve the corrosion resistance of the alloy; after the rough tube is formed, annealing is carried out to eliminate internal stress and then surface treatment is carried out, including passivation and roller-coating the anticorrosive coating;

[0023] 2. The passivation treatment introduces a ZIF structure on the surface of the rough tube. On the one hand, it provides a corrosion inhibition effect and is tightly combined with the alloy substrate; on the other hand, it improves the adhesion of the anticorrosive coating, slows down the peeling of the coating under seawater scouring, and extends the anticorrosion time; two passivation solutions with different concentration components are used, and passivation solution b is amino-modified and multiple passivation treatments are carried out to improve the density of the passivation film and the interfacial bonding strength with the anticorrosive coating;

[0024] 3. Rosin amine is introduced into the anticorrosive coating to endow the anticorrosive coating with antibacterial and antifouling properties; modified graphene is obtained by polymerizing reduced graphene oxide, paraformaldehyde, rosin amine and urushiol and incorporated into polyurethane to improve the dispersion of graphene. The protective effect of the coating is improved by the synergy of the characteristics of polyurethane itself and the strengthening effect of graphene, and the service life of the stepped tube is extended. Detailed implementation manners

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0026] In the experiment, the preparation process of the stepped blank tube is as follows: Take a copper-nickel alloy ingot and place it in a vacuum melting furnace. Add nickel-calcium master alloy, aluminum-lanthanum master alloy, and iron sulfide for smelting. Use the semi-continuous casting process to cast a round billet. After boring, perform homogenization treatment. After holding at 950 °C for 3 h, obtain a tube through hot extrusion. After cold rolling the tube, perform full annealing at 750 °C for 2 h of heat preservation, straighten to obtain an alloy tube blank, cut it into tube segments of the required size according to the design requirements, load it into a forming die, use a push rod to push the blank into the forming channel, and gradually extrude until the push rod disengages from the forming channel to obtain the stepped blank tube;

[0027] Among them, the chemical composition of the alloy tube blank is by mass percentage: Ni 10.45%, Fe 1.73%, Mn 0.72%, Al 0.44%, La 0.03%, C 0.0003%, Pb 0.002%, S 0.0012%, P 0.001%, and the balance is Cu and unavoidable impurities.

[0028] The particle size D50 of graphene oxide is 10 - 20 μm, purchased from Changzhou Sixth Element Materials Technology;

[0029] Paraformaldehyde is purchased from Shanghai Aladdin, with the number C104188; the polyether polyol is HSH-220, purchased from Jiangsu Haian Petrochemical Factory; the silane coupling agent is KH560;

[0030] Example 1: This example provides a preparation process for an integrally formed stepped tube, and the specific steps are as follows:

[0031] Anneal the stepped blank tube, place it in a high-temperature furnace, set the temperature to 650 °C for 1 h of heat preservation, air-cool to room temperature, then take it out for polishing and cleaning. Immerse it in passivation solution a for 30 min, then take it out for cleaning and drying. Then immerse it in passivation solution b for 30 min, take it out for cleaning and drying. Then immerse it in passivation solution b for 1 h, clean and dry, and then roll-coat an anti-corrosion coating on the inner and outer surfaces of the tube, control the film thickness to be 200 μm, and cure at 60 °C for 12 h to obtain the stepped tube.

[0032] The preparation steps of passivation solution a are as follows: Take 50 mL each of 0.01 g / mL zinc nitrate hexahydrate aqueous solution and 0.025 g / mL 2-methylimidazole aqueous solution, mix and stir for 30 min to obtain passivation solution a;

[0033] The preparation steps of passivation solution b are as follows: Dissolve 0.803 g of 2-methylimidazole and 0.072 g of 2-aminobenzimidazole in 50 mL of deionized water, add 50 mL of 0.01 g / mL zinc nitrate hexahydrate aqueous solution, and mix and stir for 30 min to obtain passivation solution b;

[0034] The preparation steps of the anti-corrosion coating are as follows:

[0035] Step s1: Take 0.5 g of graphene oxide and place it in 100 mL of deionized water. After ultrasonic stirring for 1 h, add 10 mL of hydrazine hydrate and mix. Dropwise add ammonia water to adjust the pH to 10. Heat to 95 °C and stir for 5 h. After suction filtration, freeze-dry to obtain reduced graphene oxide. Transfer it to 15 mL of urushiol, ultrasonic stir for 1 h, then add 4.475 g of paraformaldehyde and 15.731 g of rosin amine and mix. Heat to 90 °C, keep warm and stir for 1 h to obtain modified graphene;

[0036] Step s2: Take 3 g of the modified graphene prepared in step s1, add 10 mL of polyether polyol and 0.2 g of silane coupling agent and mix and stir for 30 min. Then add 15 mL of isophorone diisocyanate, heat to 70 °C and preheat for 30 min. Then add 0.03 g of dibutyltin dilaurate and continue to react for 2 h. Cool to room temperature to obtain the anticorrosive coating.

[0037] Example 2: This example provides a preparation process of an integrally formed reduced-diameter pipe. The specific steps are as follows:

[0038] Anneal the reduced-diameter blank pipe. Place it in a high-temperature furnace, set the temperature to 500 °C and keep warm for 1 h. After air-cooling to room temperature, take it out for polishing and cleaning. Immerse it in passivation solution a for 30 min, then take it out for cleaning and drying. Then immerse it in passivation solution b for 30 min, take it out for cleaning and drying. Then immerse it in passivation solution b for 1 h, clean and dry, and then roll-coat the anticorrosive coating on the inner and outer surfaces of the pipe, control the film thickness to be 200 μm, and cure at 60 °C for 12 h to obtain the reduced-diameter pipe.

[0039] The preparation steps of passivation solution a are as follows: Take 50 mL each of 0.01 g / mL zinc nitrate hexahydrate aqueous solution and 0.022 g / mL 2-methylimidazole aqueous solution, mix and stir for 30 min to obtain passivation solution a;

[0040] The preparation steps of passivation solution b are as follows: Dissolve 0.785 g of 2-methylimidazole and 0.054 g of 2-aminobenzimidazole in 50 mL of deionized water, add 50 mL of 0.01 g / mL zinc nitrate hexahydrate aqueous solution and mix and stir for 30 min to obtain passivation solution b;

[0041] The preparation steps of the anticorrosive coating are as follows:

[0042] Step s1: Take 0.5 g of graphene oxide and place it in 100 mL of deionized water. After ultrasonic stirring for 1 h, add 10 mL of hydrazine hydrate and mix. Dropwise add ammonia water to adjust the pH to 10. Heat to 95 °C and stir for 5 h. After suction filtration, freeze-dry to obtain reduced graphene oxide. Transfer it to 15 mL of urushiol, ultrasonic stir for 1 h, then add 3.841 g of paraformaldehyde and 15.173 g of rosin amine and mix. Heat to 90 °C, keep warm and stir for 1 h to obtain modified graphene;

[0043] Step s2: Take 1.5 g of the modified graphene prepared in step s1, add 10 mL of polyether polyol and 0.2 g of silane coupling agent, mix and stir for 30 min, then add 10 mL of isophorone diisocyanate. After preheating at 70 °C for 30 min, add 0.03 g of dibutyltin dilaurate and continue to react for 2 h. Cool to room temperature to obtain the anticorrosive coating.

[0044] Example 3: This example provides a preparation process for an integrally formed reduced-diameter pipe, and the specific steps are as follows:

[0045] Anneal the reduced-diameter blank pipe, place it in a high-temperature furnace, set the temperature to 650 °C and hold for 1 h. After air-cooling to room temperature, take it out for polishing and cleaning. Immerse it in passivation solution a for 30 min, then take it out, wash and dry. Then immerse it in passivation solution b for 30 min, take it out, wash and dry. Then immerse it in passivation solution b for 1 h, wash and dry, and then roll-coat the anticorrosive coating on the inner and outer surfaces of the pipe, control the film thickness to be 200 μm, and cure at 60 °C for 12 h to obtain the reduced-diameter pipe.

[0046] The preparation steps of passivation solution a are as follows: Take 50 mL of 0.01 g / mL zinc nitrate hexahydrate aqueous solution and 50 mL of 0.03 g / mL 2-methylimidazole aqueous solution, mix and stir for 30 min to obtain passivation solution a;

[0047] The preparation steps of passivation solution b are as follows: Dissolve 0.982 g of 2-methylimidazole and 0.142 g of 2-aminobenzimidazole in 50 mL of deionized water, add 50 mL of 0.01 g / mL zinc nitrate hexahydrate aqueous solution, mix and stir for 30 min to obtain passivation solution b;

[0048] The preparation steps of the anticorrosive coating are as follows:

[0049] Step s1: Take 0.5 g of graphene oxide and place it in 100 mL of deionized water. After ultrasonic stirring for 1 h, add 10 mL of hydrazine hydrate and mix. Dropwise add ammonia water to adjust the pH to 10, heat to 95 °C and stir for 5 h. After suction filtration, freeze-dry to obtain reduced graphene oxide. Transfer it to 15 mL of urushiol, after ultrasonic stirring for 1 h, add 4.975 g of paraformaldehyde and 17.931 g of rosin amine and mix, heat to 90 °C, keep warm and stir for 1 h to obtain modified graphene;

[0050] Step s2: Take 5 g of the modified graphene prepared in step s1, add 10 mL of polyether polyol and 0.2 g of silane coupling agent, mix and stir for 30 min, then add 20 mL of isophorone diisocyanate. After preheating at 70 °C for 30 min, add 0.03 g of dibutyltin dilaurate and continue to react for 2 h. Cool to room temperature to obtain the anticorrosive coating.

[0051] Example 4: This example provides a preparation process for an integrally formed reduced-diameter pipe. The specific steps are as follows:

[0052] Anneal the reduced-diameter blank pipe. Place it in a high-temperature furnace, set the temperature to 650 °C and keep it warm for 1 h. After air-cooling to room temperature, take it out for polishing and cleaning. Immerse it in passivation solution a for 30 min, then take it out for cleaning and drying. Then immerse it in passivation solution b for 30 min, take it out for cleaning and drying. Then immerse it in passivation solution b for 1 h, and after cleaning and drying, roll-coat an anti-corrosion coating on the inner and outer surfaces of the pipe, control the film thickness to be 200 μm, and cure it at 60 °C for 12 h to obtain the reduced-diameter pipe.

[0053] The preparation steps of passivation solution a are as follows: Take 50 mL each of 0.01 g / mL zinc nitrate hexahydrate aqueous solution and 0.025 g / mL 2-methylimidazole aqueous solution, mix and stir for 30 min to obtain passivation solution a;

[0054] The preparation steps of passivation solution b are as follows: Dissolve 0.903 g of 2-methylimidazole and 0.122 g of 2-aminobenzimidazole in 50 mL of deionized water, add 50 mL of 0.01 g / mL zinc nitrate hexahydrate aqueous solution, mix and stir for 30 min to obtain passivation solution b;

[0055] The preparation steps of the anti-corrosion coating are as follows:

[0056] Step s1: Take 0.5 g of graphene oxide and place it in 100 mL of deionized water. After ultrasonic stirring for 1 h, add 10 mL of hydrazine hydrate and mix. Dropwise add ammonia water to adjust the pH to 10, heat up to 95 °C and stir for 5 h. After suction filtration, freeze-dry to obtain reduced graphene oxide. Transfer it to 15 mL of urushiol, ultrasonic stir for 1 h, then add 4.547 g of paraformaldehyde and 16.731 g of rosin amine and mix. Heat to 90 °C, keep warm and stir for 1 h to obtain modified graphene;

[0057] Step s2: Take 4 g of the modified graphene prepared in step s1, add 10 mL of polyether polyol and 0.2 g of silane coupling agent, mix and stir for 30 min, then add 18 mL of isophorone diisocyanate, preheat at 70 °C for 30 min, add 0.03 g of dibutyltin dilaurate and continue to react for 2 h. Cool to room temperature to obtain the anti-corrosion coating.

[0058] Comparative Example 1: As a control experiment for Example 1, for Example 1, no modified graphene is added. The specific steps are as follows:

[0059] Anneal the stepped blank tube. Place it in a high-temperature furnace, set the temperature to 650 °C and hold for 1 h. After air-cooling to room temperature, take it out for polishing and cleaning. Immerse it in passivation solution a for 30 min, then take it out, clean and dry it. Then immerse it in passivation solution b for 30 min, take it out, clean and dry it. Then immerse it in passivation solution b for 1 h, clean and dry it, and then roll-coat an anti-corrosion coating on the inner and outer surfaces of the tube, control the film thickness to be 200 μm, and cure it at 60 °C for 12 h to obtain the stepped tube.

[0060] The preparation steps of passivation solution a are as follows: Take 50 mL each of 0.01 g / mL zinc nitrate hexahydrate aqueous solution and 0.022 g / mL 2-methylimidazole aqueous solution, mix and stir for 30 min to obtain passivation solution a;

[0061] The preparation steps of passivation solution b are as follows: Dissolve 0.803 g of 2-methylimidazole and 0.072 g of 2-aminobenzimidazole in 50 mL of deionized water, add 50 mL of 0.01 g / mL zinc nitrate hexahydrate aqueous solution, mix and stir for 30 min to obtain passivation solution b;

[0062] The preparation steps of the anti-corrosion coating are as follows:

[0063] Take 10 mL of polyether polyol and 0.2 g of silane coupling agent, mix and stir for 30 min, then add 15 mL of isophorone diisocyanate, heat to 70 °C and preheat for 30 min, then add 0.03 g of dibutyltin dilaurate and continue to react for 2 h, cool to room temperature to obtain the anti-corrosion coating.

[0064] Comparative Example 2: As a control experiment for Example 1, the order of passivation solutions a and b was adjusted for Example 1. The specific steps are as follows:

[0065] Anneal the stepped blank tube. Place it in a high-temperature furnace, set the temperature to 650 °C and hold for 1 h. After air-cooling to room temperature, take it out for polishing and cleaning. Immerse it in passivation solution b for 30 min, then take it out, clean and dry it. Then immerse it in passivation solution a for 30 min, take it out, clean and dry it. Then immerse it in passivation solution a for 1 h, clean and dry it, and then roll-coat an anti-corrosion coating on the inner and outer surfaces of the tube, control the film thickness to be 200 μm, and cure it at 60 °C for 12 h to obtain the stepped tube.

[0066] The preparation steps of passivation solution a are as follows: Take 50 mL each of 0.01 g / mL zinc nitrate hexahydrate aqueous solution and 0.025 g / mL 2-methylimidazole aqueous solution, mix and stir for 30 min to obtain passivation solution a;

[0067] The preparation steps of passivation solution b are as follows: Dissolve 0.803 g of 2-methylimidazole and 0.072 g of 2-aminobenzimidazole in 50 mL of deionized water, add 50 mL of 0.01 g / mL zinc nitrate hexahydrate aqueous solution, and mix and stir for 30 min to obtain passivation solution b; The preparation steps of the anti-corrosion coating are as follows:

[0068] Step s1: Take 0.5 g of graphene oxide and place it in 100 mL of deionized water. After ultrasonic stirring for 1 h, add 10 mL of hydrazine hydrate and mix. Dropwise add ammonia water to adjust the pH to 10, raise the temperature to 95 °C, stir for 5 h, perform suction filtration, and then freeze-dry to obtain reduced graphene oxide. Transfer it to 15 mL of urushiol, ultrasonic stir for 1 h, then add 4.475 g of paraformaldehyde and 15.731 g of rosin amine and mix. Heat to 90 °C, keep warm and stir for 1 h to obtain modified graphene;

[0069] Step s2: Take 3 g of the modified graphene prepared in step s1, add 10 mL of polyether polyol and 0.2 g of silane coupling agent, mix and stir for 30 min, then add 15 mL of isophorone diisocyanate. After preheating at 70 °C for 30 min, add 0.03 g of dibutyltin dilaurate and continue to react for 2 h. Cool to room temperature to obtain the anti-corrosion coating.

[0070] Comparative example 3: As a control experiment for Example 1, no passivation treatment was performed on Example 1. The specific steps are as follows:

[0071] Anneal the stepped blank pipe, place it in a high-temperature furnace, set the temperature to 650 °C, keep warm for 1 h, air-cool to room temperature, then take it out, polish and clean it. After drying, roll-coat the anti-corrosion coating on the inner and outer surfaces of the pipe, control the film thickness to be 200 μm, and cure at 60 °C for 12 h to obtain the stepped pipe.

[0072] The preparation steps of the anti-corrosion coating are as follows:

[0073] Step s1: Take 0.5 g of graphene oxide and place it in 100 mL of deionized water. After ultrasonic stirring for 1 h, add 10 mL of hydrazine hydrate and mix. Dropwise add ammonia water to adjust the pH to 10, raise the temperature to 95 °C, stir for 5 h, perform suction filtration, and then freeze-dry to obtain reduced graphene oxide. Transfer it to 15 mL of urushiol, ultrasonic stir for 1 h, then add 4.475 g of paraformaldehyde and 15.731 g rosin amine and mix. Heat to 90 °C, keep warm and stir for 1 h to obtain modified graphene;

[0074] Step s2: Take 3 g of the modified graphene prepared in step s1, add 10 mL of polyether polyol and 0.2 g of silane coupling agent, mix and stir for 30 min, then add 15 mL of isophorone diisocyanate. After preheating at 70 °C for 30 min, add 0.03 g of dibutyltin dilaurate and continue to react for 2 h. Cool to room temperature to obtain the anti-corrosion coating.

[0075] Detection test

[0076] 1. Adhesion test: Use AB super glue to adhere the weight column to the surface of the stepped pipes prepared in Examples 1-4 and Comparative Examples 1-3. Cut along the bottom of the weight column with a blade to ensure that the scratch penetrates into the substrate. Use a paint film adhesion tester to conduct the adhesion test, and record the data in Table 1;

[0077] 2. Erosion resistance test: Use an aqueous sodium chloride solution with a mass fraction of 3.5% as the erosion medium. Spray it onto the inner and outer surfaces of the pipe at a flow rate of 3 m / s under normal temperature and pressure. After 3 days of erosion, record the change rate of the coating thickness on the surface of the stepped pipe.

[0078] 3. Salt spray corrosion resistance: Conduct the neutral salt spray performance test in accordance with GB / T 1771. In a 5wt% saline salt spray environment, set the temperature in the salt spray chamber to 35°C and record the time when rust spots appear on the stepped pipe;

[0079] Table 1

[0080] Project Adhesion strength (MPa) Erosion thickness change rate (%) Salt spray resistance time (h) Example 1 8.06 6.64 408 Example 2 7.28 7.49 336 Example 3 7.85 7.14 360 Example 4 7.43 7.22 384 Comparative Example 1 7.99 10.38 248 Comparative Example 2 7.15 7.85 402 Comparative Example 3 4.35 22.41 394

[0081] Conclusion: From the above data, it can be seen that Comparative Example 1 has better performance than the other examples; as a control experiment for Example 1, Comparative Example 1 does not add graphene oxide, and its erosion resistance and salt spray corrosion resistance decrease significantly; as a control experiment for Example 1, Comparative Example 2 adjusts the order of the passivation layer, which has a certain impact on the adhesion of the coating and also reduces the erosion resistance; Comparative Example 3 does not undergo passivation treatment, resulting in a significant decrease in the adhesion of the coating and also having a great impact on the erosion resistance.

[0082] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention.

Claims

1. A process for preparing an integrally formed reducer pipe, characterized in that: The specific preparation process is as follows: Step 1: taking a copper-nickel alloy ingot and placing it in a vacuum melting furnace, adding a nickel-calcium master alloy, an aluminum-lanthanum master alloy and iron sulfide for smelting, using a semi-continuous casting process to cast a round billet, boring it and then performing a homogenization treatment, and then hot extruding it to obtain a pipe, cold rolling the pipe and then completely annealing and straightening it to obtain an alloy pipe billet; Step 2: Cut the alloy tube blank prepared in step 1 into tube sections, load them into a forming die, use a push rod to push the blank into a forming channel, and gradually squeeze until the push rod is separated from the forming channel to obtain a reduced diameter blank tube; Step 3: After annealing the reduced diameter blank tube prepared in step 2, polish and clean it, immerse it in passivation solution a for 30 minutes, take it out, clean and dry it, immerse it in passivation solution b for 30 minutes, take it out, clean and dry it, immerse it in passivation solution b for 1-2 hours, clean and dry it, roll-coat the anti-corrosion coating on the inner and outer surfaces of the tube, and solidify it to obtain the reduced diameter tube.

2. The process for preparing an integrally formed reducer according to claim 1, characterized in that: The chemical composition of the alloy tube prepared in step 1 is calculated by mass percentage as follows: Ni 10.2-10.6%, Fe 1.6-1.8%, Mn 0.5-0.8%, Al 0.2-0.5%, La 0.01-0.05%, C < 0.0005%, Pb < 0.005%, S < 0.002%, P < 0.003%, and the balance is Cu and unavoidable impurities.

3. The process for preparing an integrally formed reducer according to claim 1, characterized in that: In step 1, the homogenization temperature is 800-950° C., and the temperature is kept for 2-3 hours; the complete annealing temperature is 700-750° C., and the temperature is kept for 1-2 hours; in step 3, the annealing temperature is 400-650° C., and the temperature is kept for 1-2 hours, and then air-cooled to room temperature.

4. The process for preparing an integrally formed reducer according to claim 1, characterized in that: The preparation steps of passivation solution a in step 3 are as follows: mixing zinc nitrate hexahydrate aqueous solution and 2-methylimidazole aqueous solution and stirring for 30 minutes to obtain passivation solution a; the mass concentration ratio of zinc nitrate hexahydrate and 2-methylimidazole in passivation solution a is 1:(2-3).

5. The process for preparing an integrally formed reducer according to claim 1, characterized in that: The preparation steps of the passivation solution b in step 3 are as follows: dissolving 2-methylimidazole and 2-aminobenzimidazole in deionized water, adding a hexahydrate zinc nitrate aqueous solution and mixing and stirring for 30 minutes to obtain a passivation solution b; the mass concentration ratio of the hexahydrate zinc nitrate, 2-methylimidazole and 2-aminobenzimidazole in the passivation solution b is 1: (1.5-2): (0.1-0.3).

6. The process for preparing an integrally formed reducer according to claim 1, characterized in that: The preparation steps of anti-corrosion coating are as follows: Step s1: placing graphene oxide in deionized water and ultrasonically stirring for 1 hour, then adding hydrazine hydrate to mix, dropping ammonia water to adjust the pH to 10, heating to 95° C. and stirring for 5 hours, filtering and freeze-drying to obtain reduced graphene oxide, transferring to urushiol, ultrasonically stirring for 1 hour, then adding paraformaldehyde and rosin amine to mix, heating to 90-95° C., keeping warm and stirring for 1 hour, to obtain modified graphene; Step s2: Take the modified graphene prepared in step 1, add polyether polyol and silane coupling agent, mix and stir for 30 minutes, add isophorone diisocyanate, heat to 70-80°C and preheat for 30 minutes, add dibutyltin dilaurate and continue to react for 2-3 hours, cool to room temperature, and obtain the anti-corrosion coating.

7. The process for preparing an integrally formed reducer pipe according to claim 6, characterized in that: In step s1, the dosage ratio of polyformaldehyde, rosin amine and urushiol is (3-5) g: (15-18) g: 15 mL, and the added amount of reduced graphene oxide is 2-5 wt% of urushiol; in step s2, the volume ratio of polyether polyol and isophorone diisocyanate is 1: (1-2); and the added amount of modified graphene is 6-15 wt% of the anti-corrosion coating.

8. The process for preparing an integrally formed reducer according to claim 1, characterized in that: The curing process parameters are curing at 60°C for 12 hours; when rolling the anti-corrosion coating, the film thickness is controlled to be 100-200μm.

9. An integrally formed reducer, characterized in that: The product is obtained by the preparation process described in claim 1.